This invention relates to pneumatic tires, and more particularly, to an improved pneumatic tire for use in snow and ice. The tread portion of a pneumatic tire as it travels through the footprint of the tire experiences many different forces. The principal lateral force experienced by the tread portion of the tire under normal dry road conditions is the longitudinal force parallel to the direction of travel of the tire. The lateral force experienced by the tread portion on dry pavement is generally too small in comparison to the longitudinal force to be of any major consequence. However, when the tire is used on snow or ice-covered roads, the coefficient of friction between the tread portion of the tire and the road surface is substantially reduced, thereby increasing the importance of lateral stability of the tread portion of the tire.
Applicants have developed an improved tire for use on snow and ice-covered roads which has improved lateral stability and gripping action. A tire made in accordance with the present invention is provided with a plurality of spaced independent projections about the tread portion of the tire. Each projection has an outer configuration which is substantially polygonal as viewed in a plane perpendicular to the tread portion. Each projection is further provided with a recessed portion approximately in the center of the projection to form an inside contour substantially identical to the outside contour of the projection. A plurality of blades or sipes extend from the recessed portion of each projection substantially radially outward to the outside surface so as to divide the independent projection preferably into a plurality of substantially identically shaped sub-elements.